Syringe Coupling Torque Limiting Lug Threads
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Solution Overview
Problem
Current two-component syringe systems for medications often experience improper mixing due to the male syringe coupler extending into the female syringe cavity, creating dead spaces and potential syringe failure from overtightening, especially when using cyclic olefin copolymers, which become brittle upon irradiation.
Innovation Solution
The female syringe features a lug-type thread configuration and an extended-length neck to prevent the male syringe coupler from protruding into the cavity, along with a tapered interface that 'slips' to release excess torque, ensuring proper mixing and preventing syringe breakage, and can be made from materials like polyethylene to replace polypropylene for cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the male syringe coupler is made longer to ensure secure coupling, then the coupling strength is improved, but the male coupler extends into the female syringe cavity creating dead spaces that impede proper mixing
Solution Approach 1:
The male coupler is segmented into two functional zones: a longer outer portion that provides secure coupling engagement with the female coupler, and a shorter inner portion that terminates before entering the female syringe cavity. This segmentation allows the coupler to fulfill both coupling and mixing functions without compromise.
Solution Approach 2:
Instead of making the entire male coupler longer to ensure secure coupling, the invention inverts the approach by providing a longer outer coupling portion while keeping the inner cavity-entry portion shorter. This inverted design prevents dead space formation while maintaining coupling strength.
2Reliability
If COC/COP material is used for the syringe to prevent solvent leaching, then the chemical stability is improved, but the syringe becomes more brittle and may fail during assembly
Solution Approach 1:
The lug thread geometry parameters are specifically optimized for COC/COP material properties. The lug width, thread pitch, and engagement depth are adjusted to accommodate the brittle nature of COC/COP, reducing stress concentration and preventing assembly-induced breakage while maintaining chemical stability.
Solution Approach 2:
The coupling mechanism uses a composite approach combining the lug thread design with the COC/COP material properties, creating a system where the thread geometry compensates for material brittleness. The lug threads are designed with rounded edges and gradual transitions to prevent stress concentration in the brittle COC/COP material.
3Strength
If lug threads are overtightened to ensure secure coupling, then the coupling strength is improved, but excess torque causes syringe breakage especially in COC/COP materials
Solution Approach 1:
The lug thread design incorporates inherent torque-limiting features that cushion against overtightening. The lug geometry and thread profile are designed to naturally limit the maximum torque that can be applied, preventing excess force transmission to the syringe body before the coupling is adequately secured.
Solution Approach 2:
The coupling mechanism is self-regulating through its lug thread design. As the coupling is tightened, the lug geometry automatically prevents further torque transmission once optimal engagement is achieved, eliminating the need for external torque control mechanisms and preventing user-induced overtightening damage.
4Ease of manufacture
If polypropylene is used for the syringe due to its low cost and pliability, then the manufacturing cost is reduced, but solvents leach through the material under long term storage
Solution Approach 1:
The syringe system employs COC/COP material that combines the necessary chemical resistance to prevent solvent leaching with adequate mechanical properties for syringe functionality. While more expensive than polypropylene, the material provides reliable long-term storage performance without solvent contamination.
Data Source
AI summary
A medication component mixing system is formed of a first syringe, such as a female syringe, and a second syringe such as a male syringe, wherein the system is configured to mix a female portion and a male portion of the medication. The female syringe and the male syringe mechanically couple to one another in an end-to-end fashion for mixing of the contents of the female and male portions.